Apparatus for forming an inhomogeneous optical layer

Abstract

An inhomogeneous optical layer is formed on a surface of a substrate in a vacuum coater, in which the substrate is moved along a travelling path having path sections and a substance is evaporated from its source and deposited on the surface while the deposited substance is exposed to gas which is able to react on the substance. In such an operation, the deposition rate of the substance is varied monotonously along the path in each of the path section in order that, in a layer formed by the deposition on the substrate, the content of the substance and that of the reaction product are varied monotonously in the direction of thickness. If the refractive index of the substance is different from that of the reaction product, the resultant refractive index in the layer is varied monotonously in the direction of the thickness of the layer.

We claim: 
     
       1. An apparatus for forming an inhomogeneous optical layer on a surface of a substrate comprising a vacuum vessel, means for moving the substrate along a travelling path in the vacuum vessel, said travelling path having a path section or a number of path sections, source means for evaporating an evaporation substance in the vacuum vessel, deposition rate regulating means for causing the evaporation substance evaporated from the source means to be deposited on the surface of the substrate moving along the travelling path with the depositing rate being varied monotonously along the travelling path in the path section or each of the path sections, and exposure means for causing the deposited evaporation substance to be exposed to reaction gas which is able to react on the evaporation substance. 
     
     
       2. An apparatus according to claim 1 wherein the deposition rate regulating means is constructed by shader means which shades the evaporation substance evaporated from the source means and flying in the vacuum vessel so that the incident angle of the evaporation substance is varied monotonously along the travelling path in the path section or each of the path sections. 
     
     
       3. An apparatus according to claim 1 or 2 wherein the exposure means is so arranged that the incident density of the reaction gas is varied monotonously along the travelling path in the path section or each of the path sections. 
     
     
       4. An apparatus according to claim 3 the depositing means is constructed by means for introducing the reaction gas into the vacuum vessel so that the incident density of the reaction gas is varied monotonously along the travelling path in the path section or each of the path sections.